In the prior art many means have been proposed to apply, on the bearings, forces known as compensation forces, and more often the prior art provides the confinement of the compensation chambers between the bearings and the covers closing the pump or motor housing on its lateral sides.
In some publications, for example in U.S. Pat. No. 3,473,476, compensation chambers are delimited by walls engaging in grooves, the walls being somewhat used as sealing means between the bearings and the covers. The same has been proposed in French Pat. No. 1,598,392 which shows seals disposed in grooves of the pump or motor housing, these seals delimiting complex-shaped chambers in which some fluid is pressure-loaded with a pressure corresponding to that which operates on the opposite face of the bearing, that is to say the face directed towards the gears.
Other publications show other similar seals and chambers. It is the case, in particular, of U.S. Pat. Nos. 3,482,524 and 3,142,260.
Applicant has shown, particularly in French Pat. No. 73 02257 published under No. 2,215,103, a similar arrangement in which a seal is provided either in the bearings, or in the cover in order to delimit compensation chambers.
The foregoing arrangements are generally satisfactory but have proved to be imperfect for hydraulic pumps or motors working under very high pressure. Actually, the seals as well as the walls for maintaining the seals are generally fragile members. Moreover, when provided, walls limit the surface on which the compensation pressure can operate.
The present invention resolves this problem by enabling the exertion of compensation pressures on the whole useful surface of the bearings of a pump or a motor, and in this whatever the rotary direction of the gears.